A free (libre), open-source (GNU GPL) blogging and content-management system. WordPress is written in PHP, supports severeal operating-systems, and requires a MySQL database.
Notable WordPress sites include the U.S. Library of Congress, MSNBC, and The Rolling Stones.

A free (libre), open-source (GNU GPL) content management framework written in PHP with support for a number of operating-systems, web-servers and databases.
Drupal made international news following the U.S. White House's October 2009 web redesign. The variety of Drupal-powered websites demonstrates the platform's flexibility. Notable examples include British Medical Journal (BMJ); Stanford Law School, and Turner Broadcasting.